to the capture, of the mastermind of the September 11 attacks on the United States.
Critics of Bush's "global war on terror" have accused him of putting too much emphasis on Iraq, which had no known connection to the September 11 attacks, at the expense of efforts to get Bin Laden and dismantle Al-Qaeda.
Shortly after the September 11 attacks, Bush said he wanted Bin Laden caught, dead or alive. But a year before the 2003 US invasion of Iraq, Bush's emphasis shifted, saying he did not know bin Laden's whereabouts and "I truly am not that concerned about him."
The White House had no comment on the Senate legislation, which also needs to be approved by the House of Representatives and then Bush.
Sen. Kent Conrad, the North Dakota Democrat who co-authored the measure, told reporters he "has been told by people in the military it might be beneficial" to increase the bounty.
While he doubted the additional money would lure loyalists in Bin Laden's "inner circle," Conrad said it might attract those "more distantly connected" to Bin Laden, who is thought to be in a region along the Afghanistan-Pakistan border.
The Senate vote came just days after Homeland Security Secretary Michael Chertoff said he had a "gut feeling" that the United States was at greater risk of another attack, noting increased Al-Qaeda activity and a history of summer attacks.
On Thursday, Bush denied media reports, citing new intelligence assessments, that Al-Qaeda is now as great a threat to US soil as in the months before September 11.
Sen Byron Dorgan, also a North Dakota Democrat, said more important than the bounty was the legislation's requirement that the administration give Congress classified reports on the hunt for Al-Qaeda leaders every 90 days.
Those reports would assess the location of Bin Laden and other key Al-Qaeda leaders, describe efforts to capture them and gauge whether there is cooperation from countries that might have Al-Qaeda leaders on their soil.
Citing reports that Bin Laden could be in a secure hideaway in Pakistan, Dorgan said, "There should not be one square inch on this planet" that is safe for Bin Laden.
Sen. Jim Bunning, the Kentucky Republican who cast the only vote against raising the bounty, said catching Al-Qaeda leaders already was a "top priority." In a slap at Democrats, he added, "If Senator Dorgan truly supported our efforts to fight Al-Qaeda he would not support withdrawing from Iraq, a key battleground against Al-Qaeda and in the war on terror."
Top US intelligence officials informed the House of Representatives Armed Services Committee this week that inhabitants of remote northwestern Pakistan, where Bin Laden is believed to be holed up, have proved impervious to the financial rewards already on offer from the US government.
The US government says it has spent more than $62 million in a "rewards for justice" programme for various information that has helped prevent attacks or prosecute those responsible for attacks.
(Additional reporting by David Morgan and Caren Bohan)